A safety securing device of this type is disclosed in PCT/JP93/00758. Also, a sensor for verifying that the rotation or movement of a mechanical movable portion has stopped is disclosed in International Publication WO94/23303. In addition, a device for detecting that rotation is at a specific rate or lower is also required in an apparatus that includes a mechanical movable portion driven by a motor M or the like, i.e., a robot or the like, as a safety device that allows the operator to approach the apparatus only after the mechanical movable portion has completely stopped its operation, in order to assure the safety of the operator who must approach the apparatus. Such safety devices include the motor rotation stop detecting device disclosed in International Publication WO94/23303, which is capable of reliably detecting that the rotation of a motor M has stopped, including rotation under inertia, and operates toward safety when the apparatus has had a failure, thereby providing a high degree of safety. However, the device disclosed in this prior art publication has two problems yet to be solved, i.e., a delay in issuing notification of the stop that occurs because the device is not provided with a function for detecting the rotation rate and, since a bridge circuit is employed for a rotation sensor, adjustment of the bridge circuit is required.
These problems are eliminated in PCT/JP95/00165 for which an application was submitted by the applicant. However, PCT/JP95/00165 only discloses the technology for issuing notification of mechanical movable portion stop, and the disclosure does not encompass the use of the mechanical movable portion stop signal as a signal for assuring safety of an operator against the mechanical movable portion.